H01J61/0732—Main electrodes for high-pressure discharge lamps characterised by the construction of the electrode

Abstract

PURPOSE: To perform a stable discharge by forming a spherical discharge section larger in diameter than a main section at the tip of an electrode.

CONSTITUTION: A discharge section 17a protruded into a discharge space has a spherical section larger in diameter than an electrode base section 17b, and a stable discharge is performed on the whole discharge section 17a while no arc spot is concentrated at one point. An electrode 17 crosses perpendicularly to a bar-shaped body W at the tip section of the bar-shaped body W made of tungsten as shown by (a), laser rays (l) are concurrently radiated from opposite directions to each other, and the spherical discharge section 17a larger in diameter than the electrode base section 17b of a main section is formed at the tip as shown by (b). Symbols 60 indicate the laser radiation sections of a YAG laser device 26.